Heinz Weber dislosed a telescopic umbrella in his U.S. Pat. No. 4,007,752 having an umbrella stick, with a runner slidable thereon from which runner stretchers are pivoted, at the ends of which are seated dome ribs, and above each of which is located an auxiliary link running approximately parallel therewith, one end of each auxiliary link being hinged to a dome rib while the other end is hinged to a strut, said strut running, when the umbrella is in an open configuration, obliquely upwards from said slide strut towards the umbrella stick, and a control strut running from each stretcher approximately parallel with an inner dome rib part, the outer end of said control link and serving to control the folding motion of the outer dome rib part in dependence on the movement of the umbrella runner.
However, such a conventional umbrella has some technical limitations, impairing its folding motion, as shown as follows.
1. In the intermediate opening or closing phase of the umbrella, a controllable hinged parallelogram II is available between the dome rib part 86 and the control link 22. In order for increasing the effective leverage length of arm 25 for assisting the intermediate opening or closing operation, the slot 27 should be made as long as possible, thereby causing an unstable linking configuration when opening the umbrella or causing a larger volume when folding the umbrella links and ribs. If the slot 27 is made too short, the opening or closing operation of the umbrella will bear against a stronger pressure since the leverage length of arm 25 is quite limited within a shorter slot 27.
2. The folding operation of the umbrella is actuated by two parallelograms I, II, without being assisted by any resilient link or sliding mechanism, thereby causing a slow folding motion when closing the two paralellograms I, II constructed by the plural links and ribs.
The present inventor has found such drawbacks of a conventional shortenable umbrella and invented the present umbrella link means having accelerated folding operation.